Semiconductor devices include insulating films made of a material, such as SiO2, PSG (Phospho Silicate Glass), P(plasma)-SiO, P(plasma)-SiN, SOG (Spin On Glass), Si3N4 (silicon nitride), etc.
For example, Jpn. Pat. Appln. KOKAI Publication No. 11-172439 discloses a method of forming a silicon oxide film or silicon nitride film on the surface of a semiconductor wafer by thermal CVD (Chemical Vapor Deposition). In such thermal CVD, a silane family gas, such as monosilane (SiH4), dichlorosilane (SiH2Cl2), hexachlorodisilane (Si2Cl6), or bistertialbutylamino-silane (BTBAS), is used as a silicon-containing gas.
Specifically, for example, where a silicon oxide film is deposited, such a gas combination is used, as SiH4+N2O, SiH2Cl2+N2O, or TEOS (tetraethyl-orthosilicate)+O2. Where a silicon nitride film is deposited, such a gas combination is used, as SiH2Cl2+NH3, or Si2Cl6+NH3.
As described later, however, the present inventors have found that an insulating film formed by conventional film-formation methods of this kind causes a problem in a cleaning process subsequently performed. Specifically, where a lower process temperature of film-formation is used in conventional film-formation methods, the etching rate of an insulating film becomes higher, thereby bringing about lower controllability in the film thickness in the cleaning process subsequently performed.